Please remember that these are rumors and are to be taken with salt.
i just post what i've been told by GW friends, and we're not talking red shirts or just store managers. When I have thoughts of my own or personal hopes, I state them as such.
The new Codex is done, and yeah, it should be leaving the printers shortly, to be stored up in ware houses for distribution within the next couple of months. As for models, apparently 4 waves are planned...there's a lot of Chaos to be covered. With the Daemons to be redone sometime next year (2013) for both 40K and Fantasy, we'll see the new Greater Daemon models then.
Interesting that vehicle upgrades have been brought up, especially for Legion specific types of weapons, and apparently we do get some similar to the old "3.5" codex in these. Poisoned flamers for Nurgle, higher strength/lower AP for Tzeentch, sonic weaponry for Slaanesh and brutal blades for Khorne? Raptors are Night Lords, where as Assault Marines are all Legions and can be marked.
As i've already mentioned, HQs will have an affect on the types of units/marks available to your Army. IF 6th Edition returns to Percentages, the Codex will make more sense...